Novel techniques of immunology, molecular and cell biology have recently been used to gain a better understanding of Plasmodium- host interaction, and to serve as a basis for the development of effective malaria control measures, including vaccines. This research has lead to considerable progress in the last few years, but has been limited to a single human malaria parasite, Plasmodium falciparum. It is our objective to extend this research to the second most prevalent human malaria parasite, Plasmodium vivax, by initiating a molecular analysis valent human malaria parasite, Plasmodium vivax, by initiating a molecular analysis of blood stage antigens and red blood cell components involved in parasite host-cell interaction. For this purpose we will pursue the following lines of research: (1) identify the merozoite proteins of P. vivax and investigate their role in the attachment process, focusing on the interaction between parasite ligands and receptors on the erythrocyte surface; (2) identify the parasite proteins inserted into or associated with the infected erythrocyte membrane and the caveolar-vesicular complexes; (3) isolate and characterize the genes encoding selected P. vivax blood stage proteins involved in parasite interaction with host erythrocytes and the immune system. It is hoped that the proposed approaches will provide basic information for the development of anti-P. vivax blood stage vaccine candidates. Maximal protection against vivax malaria is likely to be achieved using a polyvalent vaccine protecting against several parasite antigens which can be targeted throughout the life cycle.